1. Field of the Invention
The present invention relates generally to gas flow delivery systems and, more particularly, gas flow delivery systems that utilize a respiratory mask to deliver a gas to a patient.
2. Description of the Related Art
Gas flow delivery systems are used to deliver a flow of gas to an airway of a subject. Examples of gas flow delivery systems in the medical field include a ventilator or respirator, which replaces or supplements a patient's respiration, and a pressure support system, which provides a flow of gas to an airway of a patient at an elevated pressure to treat a medical disorder, such as obstructive sleep apnea (OSA). Pressure support systems include, but are not limited, to continuous positive airway pressure (CPAP) devices, which deliver a constant positive pressure to the airway of a patient over multiple respiratory cycles, and variable pressure devices where the pressure of the flow of gas delivered to the patient is variable.
Variable pressure devices include auto-titrating devices that are capable of changing a base pressure or pressure profile delivered to the patient based on a monitored condition of the patient. Other variable pressure devices change the pressure of the flow of gas during a respiratory cycle. These devices include the following: a proportional assist ventilation (PAV®), a proportional positive airway pressure (PPAP) device, a C-Flex™ device, a Bi-Flex™ device, and a BiPAP® device manufactured and distributed by Respironics, Inc. of Pittsburgh, Pa. The BiPAP® device is a bi-level pressure support system in which the pressure provided to the patient varies with the patient's respiratory cycle so that a higher pressure is delivered during inspiration than during expiration.
A typical gas flow delivery system comprises a pressure/flow generating system that produces a flow of gas for delivery to a patient and a system for communicating the flow of gas to the patient. The latter system typically includes a flexible conduit having one end coupled to the pressure/flow generating device and a second end portion that couples to an airway of the patient through a patient interface. The conduit, which is also referred to as a patient circuit, carries the flow of gas from the pressure generating device during operation of the system. The patient interface device, typically in the form of a nasal, oral, or nasal/oral mask, is coupled to the second end portion of the conduit to communicate the flow of gas from the patient circuit to the airway of the patient.
Patient interfaces utilizing an inflatable contact rim, or cuff, are generally known. In general, such rims are inflated to a desired pressure through the use of pressurizing air but remain resiliently elastic and can, therefore, conform accurately to a wearer's face. In this manner, a desired close contact between the mask and the wearer's face is achieved.
The inflatable rims typically take the form of an “inner-tube” type inflatable structure. Such inflatable rims are typically manufactured either by the folding of a unitary film or by a blow molding or “slush” molding process. Typically, no matter which process is used to form the inflatable rim, special measures (e.g., gluing or welding) are necessary for the circumferential closure of the resulting molded material, so that an isolated interior space is formed. A special closure device must be provided (see, for example, U.S. Pat. No. 3,695,264) so that the air remains in this interior space after inflating the rim, and this also increases the total cost of the mask. Finally, a further disadvantage is that the resulting mask is not always in a ready-to-use condition because the rim typically first has to be inflated and the closure device has to be actuated.
Respiratory masks having a non-gaseous “filling” substance in the rim, such as a gel or liquid, are known in the art for maintaining the rim in a constant ready-to-use condition, (e.g., held in a taut or resiliently elastic state by the filling substance). However, this type or rim has the same manufacturing disadvantages discussed previously, with only the closure device being eliminated. Finally, non-inflatable rims for respiratory masks have traditionally been manufactured by vulcanization, which is also relatively expensive. Patents disclosing various versions of each of the foregoing types of mask rim configurations are described hereinafter.
U.S. Pat. No. 790,057 discloses an early inhaler anesthesia mask having a generally inward curvature with an adaptation for the bridge of the nose of a patient. U.S. Pat. No. 1,206,045 discloses a nasal inhaler with a hard, gas tight support shell with a “flange” formed of plastic material situated between the shell and the patient as a sealing means. U.S. Pat. No. 2,313,999 generally discloses a double-shelled mask formed from flexible rubber. U.S. Pat. Nos. 2,535,938; 2,625,155; 2,765,788; and 3,042,035 generally disclose masks with a relatively hard material forming the sealing flange of the mask. The downward pressure applied to the masks disclosed by these patents tends to increase the seal between the wearer's face and the flange by causing a reaction of opposing skin and muscles, but with increasing discomfort to the wearer. U.S. Pat. No. 2,875,757 discloses an inflatable cuff type mask with an inflation valve.
U.S. Pat. No. 4,062,357 discloses a modern version of a mask with an inflatable rim. The mask disclosed by this patent includes a faceplate and an air-filled cushion rim attached to the faceplate. U.S. Pat. No. 4,201,205 discloses an oxygen mask with a flexible clear plastic shell having a flange for improving the seal between the mask and the wearer's face. U.S. Pat. No. 4,347,205 discloses an inflatable rim with a dual lumen configuration. U.S. Pat. No. 4,803,981 discloses a nose inhaler having only a firm rubber foam material for engaging the wearer's nose. U.S. Pat. No. 4,807,617 discloses a scavenging mask that cooperates with a mask having an inflatable rim. U.S. Pat. No. 4,913,401 discloses a valve assembly generally representative of inflating valves for inflatable rims. U.S. Pat. No. 4,971,051 discloses a CPAP device with an inflatable rim that is inflated under air pressure provided by a balloon.
U.S. Design Pat. No. D293,613 discloses an inflatable rim type mask with an inflating valve located at the nose bridge area. U.S. Design Pat. No. D323,908 discloses an inflatable rim type mask with an extension of the support shell or base located just superior to the bridge of the nose, for supporting one or more fingers of an anesthesiologist or nurse during use.
U.S. Pat. No. 5,121,745 shows an inflatable rim-type mask adapted specifically for use in CPR applications and which is collapsible to a thin profile when not in use.
U.S. Pat. No. 5,738,094 discloses a mask with an inflatable rim generally including a faceplate with a circumferential rim or flange and an air-fillable rim adhered or otherwise secured to the flange of the faceplate. U.S. Pat. No. 6,408,853 discloses a mask with an inflatable rim generally similar to that disclosed by U.S. Pat. No. 5,738,852, but further discloses a method of forming the inflatable rim so that the rim may have an increased wall thickness on the flange facing side of the rim and a thinner wall thickness on the patient facing side of the rim. Finally, U.S. Pat. No. 6,834,650 discloses a face or nose mask with two annular chambers forming a cushion rim. Each of the chambers is air-inflatable and may be continuously pressurized by an external air source.
In view of the foregoing, a need generally exists for an improved respiratory mask in which the components of the mask are easy to manufacture thereby facilitating assembly of the mask. Additionally, a need exists for a respiratory mask that is easy to don and adjust and is comfortable to the wearer. Further, a specific need exists for a respiratory mask having an inflatable contact rim or cushion that exhibits improved sealing characteristics, is easy to inflate and deflate, and which can establish and maintain desired inflation pressures.